1. Field of the Invention
The present invention concerns an ejector for sucking a fluid by utilizing a negative pressure formed by the involving effect of a jet stream jetted at a high speed, a fine solids recovery apparatus using the ejector and a fluid conveyor.
2. Statement Related Art
In recent years, numerical control (NC) systems have been progressed in machine tools for cutting or machining metal works and most of processes from setting of works and machine tools to the completion of the cutting or machining operation have been conducted automatically.
In this case, since a great amount of cuttings (e.g., a lot of machining chips) are discharged, if left as they are, they not only hinder the cutting or machining operation but also twine around the works or tools under rotation, to injure the works or scatter the cuttings to the surroundings (or the machining chips around the machine).
In view of the above, it has been adopted, upon cutting or machining works, a method of flowing cuttings or machining chips together with lubricants and cutting oils (e.g., coolant) used as cooling liquids into buckets located below machine tools or the machine, recovering the cuttings or the machining chips in the stream of the cutting oils (e.g., coolant) recovered from the buckets by way of waste oil flow channels or flumes (troughs) and then separating the cutting oils (e.g., coolant) and the cuttings or machining chips by solid/liquid separation.
The recovered cutting oils (e.g., coolant) are circulated and re-utilized but they have to be disposed finally as industrial wastes which is not desirable in view of environmental protection. Then, dry process of conducting the cutting or machining operation by using super hard bites with no use of cutting oils (e.g., coolant) has become predominant in recent years.
In this case, generally, the cuttings or machining chips are at first blown out by an air stream jetted out from an air nozzle (e.g., a compressed air stream) disposed near the tool and dropped into a bucket located below a machine tool or machine, and then cuttings or machining chips are conveyed to a predetermined place for recovery in a plant by way of a conveying channel or route comprising a plurality of belt conveyors connected to each other.
However, since individual belt conveyors constitutes each a linear conveying path, when a plurality of belt conveyors are connected, the conveying paths are formed in a polygonal line which makes a free layout difficult and increases the installation cost, as well as gives rise to a problem of increasing the running cost since individual conveyors require driving motors respectively.
Further, it also involves a problem of tending to cause failure when fine cuttings or chips and the likes clog the mechanical driving portion of the belt conveyor.
When a pneumatic conveyor is used instead of the belt conveyor and cuttings or machining chips are sucked like in a vacuum cleaner and then conveyed on an air stream, since the conveying path itself is a pipe, it can be arranged in a free layout. However, when a mechanical vacuum pump is used as a driving source for the pneumatic conveyor, it also requires increased installation cost and running cost and there is also a worry that cuttings or fine chips clog the vacuum pump.
Then, when an ejector is used instead of the vacuum pump, the installation cost is decreased, both of the driving source and the conveying path are free from the provision of mechanical driving portions at all, and high pressure or compressed air referred to as “plant air” supplied from pipelines in the plant may be used as the energy therefor, so that the running cost can also be decreased.
However, since the ejector has an extremely low negative pressure compared with the reciprocal, rotational or centrifugal mechanical vacuum pump, although it may be used as a driving source for a pneumatic conveyor that conveys light-weight material such as powder, it can not be practical as a driving source for a pneumatic conveyor that conveys fine metal pieces such as cuttings or machining chips.
Further, the ejector is used also as a driving source for a fluid conveyor that jets out a liquid such as water to form a jet stream, sucks the fluid of a similar type by the negative pressure and conveys burnt ashes such as clinker entrained on the fluid flow. In this case, if a higher negative pressure can be obtained, the suction amount can be increased to improve the conveying efficiency by so much, can serve to energy saving and also decrease the running cost.
In view of the above, if an ejector is used, for example, as a driving source for a fluid conveyor, etc., the present invention is configured to increase the negative pressure and increase the ejector power, by improving the conveying efficiency, serving to energy saving and also reducing the running cost.